1. Field of the Invention
The present invention relates to a dynamic characteristic calculation apparatus and method thereof calculating a dynamic characteristic of a tool tip of a rotational tool in a vibration system, in which the tool tip of the rotational tool is a vibration body, in a machine tool executing a machining by the rotational tool of an end mill and so on.
2. Description of the Related Art
It is important for deciding a proper machining condition to identify dynamic characteristic of a machine tool in order to high precision machining by a rotational tool of an end mill and so on. In a prior art of US2010/0305898 A1, it is disclosed a dynamic rigidity calculation of a spindle by detecting an amount of run-out of an un-balance master that is equipped on the spindle. In another prior art of Japanese Laid-open Publication Tokkai-Hei 11-19850, it is disclosed a dynamic rigidity measurement of a spindle by measuring a displacement of measured target with means of exciting to vibrate the measured target of a spindle, a tool or a dummy tool mounted on the spindle etc. by magnetic attraction of a magnet. A displacement sensor is disclosed to be an eddy current displacement sensor, an inductance displacement sensor, an optical displacement sensor, a capacitance displacement sensor and so on.
On the other hand, since it tends to use a smaller rotational tool with a longer protruding amount of the rotational tool for higher accurate machining, an amount of deflection of the rotational tool becomes larger. Therefore, it is needed to measure dynamic characteristic in a vibration system including the rotational tool because it is not sufficient to measure the dynamic rigidity of the spindle itself as shown in the prior arts. It is hard to obtain the dynamic characteristic in a state that the dummy tool is mounted on the spindle in the prior art. The eddy current displacement sensor should be installed precisely, thereby increasing the installing time.